A mucus layer present at various points of entry into the body, including the eyes, nose, lungs, gastrointestinal tract, and female reproductive tract, is naturally adhesive and serves to protect the body against pathogens, allergens, and debris by effectively trapping and quickly removing them via mucus turnover. For effective delivery of therapeutic, diagnostic, or imaging particles via mucus membranes, the particles must be able to readily penetrate the mucus layer to avoid mucus adhesion and rapid mucus clearance. Particles (including microparticles and nanoparticles) that incorporate pharmaceutical agents are particularly useful for ophthalmic applications. However, often it is difficult for administered particles to be delivered to an eye tissue in effective amounts due to rapid clearance and/or other reasons. Accordingly, new methods and compositions for administration (e.g., topical application or direct injection) of pharmaceutical agents to the eye would be beneficial.